Spark plug



March 27, 1928.

J. G. DICKSON SPARK PLUG Filed Aug. 24. 1926 INI/ENTOR:

J4 /y/Els 6. /c/nso/v,

Patented Mar. 27, 1928.

vPATENT oFFIcE.

JAMES G. DICKSON, OF GrlAL'ENCOE,r ILLINOIS.

SPARK rLUG.

AApplication led August 24, 1926. lSerial No. 131,181.

This invention relates to that class of spark plugs in which 'anintermediate' electrode is arranged' between the sparking vterminals of the appliance, an example of which is shown in the prior Dickson Patent No. 1,414,806, of `May, 2, 1922, And the present improvementhas for its object:-

' To provide a structural formation and combination of parts Vand features in a spark plug of the above mentioned class, wherein an intermediate electrode of. a rod form is supported in a substantial manner against displacement in actual use, with such arrangement coacting with an open bottom cylindric bore Vor chamber'formed in the lower part of the plug housing by an annular depending skirt portion the bottom y face of which portion is of a plane'or flat form, in order to attain a ,maximum scouring action upon the sparking terminals and intermediate electrode, keeping same from an accumulation of carbonaceous matter and the formation of a short circuit between the parts. Such scouring action being eected by the expansion of the compressed gases in said bore or chamber of theY plug housing, all as will hereinafter more fully appear.

In the accompanying drawing: Fig. l, is an elevation of a spark plug 3o having this invention applied, the lower portion of the enclosing shell being shown in section to disclose the internal arrangement of parts.

Fig. 2, is bottom view of the same. Fig. 3, is a detail section on a plane at right angles to the plane of Fig. 1.

- Fig. 4, is a similar view of a modification.V

Like reference numerals indicate like parts in the different views.

The constructions shown of a spark plug,

is of the `generally used type in which an outer vmetallic shell is formed to screw into` an opening in the wall of an engine cylinder, with its upper portion 1 internally screw-threaded for the reception of a sleeve nut 2 by which the central core 3 of insulating material is held in place, with said core carrying one terminal point or stem 4, which in the presentinvention depends from the center of the core 3 and is deflected laterally described interme the enclosing shell l, with the inner portion of said stem projecting into the cavity of said yskirt portion 6 and deflected down wardly to have spaced relation to the intermediate electrode above referred to, 'and opposed 'relation' tothe aforesaid point or stem 4.'. v v

As usual inthe present type of spark plugs, and'more especially in the present coacting kcombination and formation of parts,v

the aforesaid annular skirt portion Gef-the shell or housing lv provides an open bottom Vwill act in an effective manner to dislodge any carbon and oil coatings upon the transversely arranged electrode, associated inwardly projecting insulating bushings andy respective vsupply and return terminals which in the present construction are located in the lower portion of said open bottom chamber.

In thefpresent improvement, the inter- A mediate electrode 7 is formed by piece of rod metal or similar conducting material,

Vextending transversely, and preferably diametrically of the cavity of the skirt portionV 6 of the enclosing shell 1, and supported in place by socket plugs or bushings 8, of insulating material, fixed in the wall of said skirt portion'G, and with the aligned socket cavities ofthe bushings receiving and supporting the respective ends of such rod electrode 7.

Usually cushions 9 of elastic ireproof material will be arranged in the bottom portions ofsuch cavities to hold said rod lelectrode from shifting endwise and at-the same time permit of differential expansion and contraction of the parts in actual use.

In the preferred construction shown in Figs. 1, 2 and 3, which is intended for engines f the medium compression type, the intermediate electrode 7 will be positioned in the skirt portion V6 immediately above a pair of diametrically opposed semicircular notches l0 formed tin the wall of such skirt portion. Such construction is intended to permit ready outward vflow of the initial iame of an explosion in an approximately horizontal plane into the combustion chamber of the engine cylinder. Such provision may however be dispensed with in spark plugs intended of engines of the high compression type, and the intermediate electrode 7 nearer the lower end or the skirtV supply terminal stein depending` within said bore, a return terminal stem-fixed at vone end in the wall of said skirt portion, and an intermediate electrode of the rod form arranged transversely in the lower end of the bore of said skirt portion and in angular relation to and inline with the aforesaid return terminal stem, said intermediate electrode being supported at its respective ends in an insulated manner in the annular wall of said skirt vportion by-individual insulat-k ing sockets 'iitted to orifices inthe wall of the laforesaid skirt portion.

2. In a spark pl-ug of the type described, the combination of an enclosing shell havinga'n annular depending skirt portion providing an open-bottom chamber at they lower end o1 the Vplug housing, the lower end of the vskirt portion having *av plane4 form, a supply terminal stem depending within said bore, a return terminal stem fixedatne end in the wall of saidY skirt portion, an Vintermediate electrode'of the rodform arranged transversely in the lowerv end oi'the kbore of said .skirt portion and in angular relation to and 1n line with ther aforesaid return terminal stem, and `insulating sockets arranged in the wallof saidskirt portion and projecting into the boreoif the-same to constitute supports for then'espective ends of the intermediate electrode at points inwardly vremote from the linneri'ace of said skirt portion. Signed at Chicago Illinois, this Y20th day or August, 1926. v

JAMES e. Dickson. 

